dtj v03-01 1991

This document is the Winter 1991 issue (Volume 3, Number 1) of the Digital Technical Journal by Digital Equipment Corporation. The primary focus of this issue is on Transaction Processing, Databases, and Fault-tolerant Systems, highlighting Digital's integrated hardware and software solutions for supporting reliable and speedy commercial applications in distributed environments.

Key areas covered include:

1. Distributed Transaction Processing Architecture (DECdta): This architecture defines the components and interfaces for Digital's transaction processing products, enabling client/server applications and ensuring reliable interoperation in distributed and heterogeneous environments. It emphasizes the critical properties of transactions: Atomicity, Serializability, and Durability (ACID).
2. Transaction Processing Monitors (ACMS and DECintact): These monitors act as "glue" for integrating various software components into a TP system. While they achieve similar goals, they differ in their application programming styles (4GL vs. 3GL) and queuing models (deferred task vs. message-based), both built upon the VMS operating system.
3. Transaction Management Support in the VMS Operating System Kernel (DECdtm): This enhancement to VMS provides base services for atomic transactions that can span multiple resource managers (databases, files) and network nodes. It implements an optimized two-phase commit protocol, leveraging VAXcluster capabilities to minimize blocking and enhance reliability.
4. Performance Evaluation and Sizing of Transaction Processing Systems: Papers detail Digital's approaches to measuring and modeling TP system performance, including the use of the industry-standard TPC Benchmark A. A multilevel analytical model is presented for performance prediction and system sizing in early development stages, translating business metrics into system resource requirements.
5. Database Availability and Optimized Transaction Commit Protocols: The journal discusses how Digital's database products (VAX Rdb/VMS, VAX DBMS), built on the KODA kernel, ensure high availability by surviving various failures (disk crashes, process failures, power outages) and minimizing downtime through recovery mechanisms and on-line operations (like backup and schema changes). It also explores optimized "group commit" protocols to significantly improve transaction throughput by amortizing disk I/O costs.
6. Verification of the First Fault-tolerant VAX System (VAXft 3000): This section describes the rigorous four-phase verification strategy, including hardware and software fault insertion, to ensure transparent system recovery from errors for applications running on the VAXft 3000 system.

In essence, the journal demonstrates Digital's comprehensive approach to building robust, high-performance, and highly available transaction processing systems, addressing challenges from core architecture and kernel support to application development, performance optimization, and fault tolerance.